Various pyrazolone derivatives are known as magenta color image forming couplers (referred to hereinafter simply as "magenta couplers"). However, these pyrazolone derivatives generally have low color forming efficiency (ratio of conversion of the coupler into a dye) when contained in photographic light-sensitive materials. In particular, known four-equivalent couplers, in which the coupling position is not substituted, have a low color forming efficiency, resulting in the conversion of only about 1/2 mol of dye per mol of the coupler present.
To improve color forming efficiency, so-called two-equivalent magenta couplers are known, in which a substituent is present at the coupling active position of a pyrazolone type magenta coupler, and the substituent is removed in the color development step.
Among these two-equivalent magenta couplers, a large number of magenta couplers are provided in which a substituent is connected to the coupling active position, through a sulfur atom as described, for example, in U.S. Pat. Nos. 3,214,437, 3,227,554, 3,701,783 and 4,032,346, Japanese Patent Publication No. 34044/78, Japanese Patent Application (OPI) Nos. 62454/80 and 35858/82 [the term "OPI" as used herein refers to a "published unexamined Japanese patent application."], etc.
It has been found that when magenta couplers capable of releasing an arylthio group present at the coupling active position as described in U.S. Pat. Nos. 3,227,554 and 3,701,783 and Japanese Patent Publication No. 34044/78, are used in a color photographic light-sensitive material and color images are formed, the light fastness of the color images is inferior. On the other hand, the couplers which release an arylthio group as described in Japanese Patent Application (OPI) No. 35858/82 certainly provide color images having improved light fastness.
However, although they represent a certain improvement over four-equivalent magenta couplers, these two-equivalent magenta couplers retain the disadvantage that stains (increase in color density in unexposed areas) are formed during development processing.
The stains occurring in unexposed areas of silver halide color photographic light-sensitive materials are undesirable and determine whether whiteness of the non-image areas is good or bad. Further, the stains adversely affect the color turbidity of the images and the visual sharpness of the images. Particularly in the case of reflective photographic materials, such as photographic color papers, the reflective density of the stains may be theoretically more increased by several times than the transmission density thereof. Therefore, such stains are very important since even a slight degree of stain can adversely affect image quality.
The stains occurring in silver halide color photographic light-sensitive materials are generally classified into four groups depending on the cause of the stain. One stain is formed after the production of the photographic light-sensitive material and before the processing thereof by exposure to heat or humidity. A second stain is caused by development fog of the silver halide. A third stain results from color contamination due to the presence of color couplers in a development processing solution (for example, aerial fog, etc.) or results from the formation of a dye by the reaction with a coupler of an oxidized developing agent, e.g., a developing agent remaining in the silver halide emulsion layer which is oxidized by a bleach solution or oxygen in the air, etc. (for example, a bleaching stain, etc.). A fourth stain results from changes in developed photographic materials with the passage of time due to light, humidity or heat. The present invention relates to stains due to the development processing of photographic materials containing 2-equivalent magenta couplers, i.e., the present invention relates to the third and fourth types of stains described above.
It is unusual to prepare a new solution for the development processing before every development processing. In practice, developing solutions are reclaimed by adding a replenishing developing solution in an amount which depends on the amount of photographic materials developed. However, the composition of a developing solution cannot be maintained merely by adding components which are consumed by development.
In general, solutions for development processing include a color developing solution, a stopping solution, a bleaching solution, and a fixing solution or a bleach-fixing (blixing) solution. Since the processing temperature is typically maintained at a high temperature of from 31.degree. C. to 43.degree. C., the compositions of the processing solutions can be changed by several factors. For example, components such as the developing agent may decompose after a long period of time or oxidize when brought in contact with the air. It is also possible for the components contained in the photographic light-sensitive materials to be dissolved and to accumulate in the solution during the processing of the photographic light-sensitive materials. In addition, one processing solution may be carried over into the following bath by becoming attached to the photographic material, by which the processing solution becomes a "running" solution. To eliminate such problems, reclaimation procedures in which depleted chemicals are supplementarily added to the solution and/or undesirable components are removed are carried out, but these procedures are still insufficient.
Photographic light-sensitive materials containing 2-equivalent magenta couplers have a notable tendency to form stains in running solutions. Moreover, the occurrence of such stains cannot be sufficiently prevented by using known arylthio releasing type couplers.
As the result of the detailed investigations, it has now been found that a series of magenta couplers exhibit remarkably reduced occurrence of stains without adversely affecting the light fastness of color images.